vMix only has support for a single SRT audio track, but does allow you to add up to 8 audio channels to this single audio track. Clevercast allows you to use this feature to broadcast a multilingual live stream of up to 8 languages using vMix. The tutorial below explains how to configure vMix and Clevercast for a live stream with 8 languages. A lower number is of course also possible.
Following this tutorial requires experience with video production and live streaming. If you don’t have this, we recommend using Translate@Home instead. If you do have the necessary experience but don’t succeed getting a live stream in Clevercast, you can contact us.
Event configuration in Clevercast
In Clevercast, press ‘Create Multilingual Event‘ and select ‘SRT Listener‘ as the broadcast protocol (so vMix can act as the SRT caller). Clevercast will create an event with your preferred default language, or ‘Original’ if the floor audio contains multiple languages.
After Clevercast has created the event, you still have to set the additional languages. In this tutorial, we’re assuming that you are sending a broadcast with 8 audio channels / languages. Go to the ‘Advanced‘ panel (at the bottom of the event page) and set the ‘Languages per track‘ setting to 8. Then select 7 ‘Additional languages‘ in addition to the default language. Note that these languages will be presented in the player in the same order as you select them.
When you’re done, press the ‘Change Event Status‘ dropdown button and set the event status to preview. This activates Clevercast’s SRT listener and is necessary for the ingest of your broadcast from vMix. For more info on event management, see §5 of our multilingual manual.
Next, we’ll use the info in the ‘Advanced‘ and ‘Broadcast’ panel (see below) to configure vMix.
1. Depending on where you get your audio from, your camera/capture card input should be set to “EmbeddedAllChannels“. We’ve verified that this works with a Blackmagic Decklink capture card.
2. Ensure you have enough audio output buses enabled in vMix settings. vMix will need to restart to apply the new settings.
3. In the audio mixer, make sure you enable all (relevant) outputs. Only bus A and B have a dedicated GUI button, so for any others you’ll need to right click on M in order to enable those as well.
4. When you go to the settings for your audio input (the little gear icon on the input in the audio mixer), you should now see all of your channels being operational in the mixer.
5. Still in the audio settings, go to the channel matrix and set them up as shown in the screenshot. Start with master L/R, then proceed with bus A L/R, bus B L/R, and so forth.
6. Now go to Settings → Outputs / NDI / SRT and click the gear on the right of output 1 (or whichever output you’re using).
7. In the Output Settings, make sure you set the Audio Channels to MABC, the maximum supported by vMix. That’s two tracks per output, i.e., two for Master, two for bus A, two for bus B, and two for bus C. Click on Enable SRT and select the ‘Caller‘ type. Fill in the ‘Hostname‘, ‘Port‘ and ‘Passphrase‘ with data from the ‘Broadcast‘ and ‘Advanced‘ panels of the Clevercast event.
Avoiding known issue: vMix sends wrong timestamps after multiple auto-reconnects
Once you click the ‘OK‘ button, vMix automatically starts broadcasting to Clevercast. Before doing this, your Clevercast event should be set to preview (or started) to activate the SRT listener in Clevercast. You can find the SRT status in vMix through the gear icon left of “External output“.
Setting the event status to waiting or ended deactivates the SRT listener in Clevercast, which causes the SRT caller in vMix to lose its connection. Unlike most SRT callers, vMix automatically tries to reestablish this connection. If this happens multiple times (e.g. by repeatedly moving the status of the Clevercast event from waiting to preview and back again) the vMix broadcast may become corrupted, which will cause the player to show a spinner.
If you reset an event to waiting or ended, it is therefore best to turn off the SRT broadcast in vMix (press External output > disabled). If your event resumes afterwards, you can simply turn the SRT broadcast in vMix back on (by pressing External output > enabled). This way you prevent this known issue from happening.